Clamp ring for a disk stack assembly

ABSTRACT

A clamp ring for a disk stack assembly of a computer disk drive unit includes a lower surface which includes an arcuate rolling contact surface that uniformly distributes a load applied to the clamp ring to components of the disk stack assembly underlying the clamp ring without damaging such disk stack components on load-induced flexion of the clamp ring. A cantilevered section of the clamp ring is disposed radially inwardly of the arcuate rolling contact surface, and is defined by a portion of the lower surface which is raised relative to an adjacent portion of the arcuate rolling contact surface so as to not contact the underlying disk stack components on load-induced flexion of the clamp ring. In use, the clamp ring is heated and then placed over the disk stack components to be clamped together. An axial load is applied to the clamp ring which causes it to flex and thus move contact between the lower surface of the clamp ring and the underlying disk stack components radially along the arcuate rolling contact surface. The axial force is maintained until the clamp ring cools sufficiently to hold the clamp ring in place, and then the axial load is removed.

This is a continuation of application Ser. No. 08/422,057, filed Apr.14, 1995, now abandoned.

BACKGROUND OF THE INVENTION

This invention relates generally to improvements in computer diskdrives. More particularly, the present invention relates to a computerdisk drive unit having a clamp ring which incorporates an arcuaterolling contact surface that prevents disk distortion during assembly ofthe clamp ring to a disk stack assembly.

In recent years microcomputer equipment, particularly personal and desktop computers, have become extremely popular for a wide variety of home,business and commercial uses. Such computers commonly include a maincentral processor unit having one or more memory storage disks. In manymodern computers, the storage disk or disks, sometimes referred to as"hard disks," are provided as part of a Winchester-type disk drive unithaving the storage disks supported in a stack on a rotary spindle withina substantially sealed disk drive housing. The disks are rotatablydriven in unison by a small spindle motor, and one or moreelectro-magnetic heads on a movable positioning arm are displaced by aprecision stepper motor to traverse surfaces of the rotating disks forpurposes of reading and writing data. Such Winchester-type disk driveunits are generally preferred in comparison with so-called floppy typedisk drives due to their higher memory storage capacities and fasteroperating speeds.

With the steadily increasing popularity of personal-sized computers,various standard computer components have evolved to accommodateinstallation into computers produced by different manufacturers and/orto ensure compatibility with commercially available software. In thisregard, Winchester-type disk drive units having one or more memorystorage disks of an approximate 5.25 inch diameter have beenmanufactured and used on an industry-wide basis. More recently, smallerand lighter Winchester-type disk drives having storage disks of about3.74 inches in diameter have become available. For either diametricsize, the disk drive units have been produced in standardized verticalprofile sizes to permit installation into a computer as an originalequipment item, or as an after-market item to replace or upgrade anoriginal disk drive unit. Disk drive units have been manufactured with avertical dimension of about 3.25 inches to fit within a so-called "fullheight" vertical spacing, or with a vertical dimension of about 1.625inches to fit within a so-called "half height" profile.

Typically, such computer disk drive units include a housing having alower base and an upper removable cover which, collectively, define adisk storage compartment therebetween. A shaft is fixed to the lowerbase and extends upwardly therefrom toward the upper housing cover, andone or more memory storage disks are mounted for rotation within thedisk storage compartment about the shaft. The shaft and the memorystorage disks comprise a memory storage unit which, with other relatedcomponents situated within the disk storage compartment, aremanufactured to very precise manufacturing specifications in order tomaximize the memory storage capabilities of the disk drive unit.

To hold the memory storage disks securely in place about the shaft, aclamp ring may be press-fit over a disk supporting hub to capture thememory storage disks and any intervening spacers between the clamp and asupporting flange. Due to the forces applied to the clamp ring duringthis assembly process, the clamp ring tends to flex, which may cause arelatively sharp corner thereof to dig into and distort the underlyingmedia. When such distortion of the underlying media occurs, the diskdrive unit may be subject to malfunction.

Accordingly, there has been a need for a novel clamp ring design andassociated assembly process that prevents disk distortion resulting fromengagement between a sharp corner of the clamp ring and the underlyingmedia during the assembly process. Such a clamp ring design should notrequire modifications in other components of the disk drive assembly,and further should be adaptable for use with existing disk clampinstallation tools. Moreover, such a clamp ring is needed which may beproduced economically, and reliably serves its intended purpose withoutthe aforementioned drawbacks of prior designs. The present inventionfulfills these needs and provides other related advantages.

SUMMARY OF THE INVENTION

The present invention resides in a clamp ring for a disk stack assemblyof a computer disk drive unit, and a related assembly process. The clampring comprises, generally, spaced-apart inner and outer walls, an uppersurface extending between the inner and outer walls, and a lower surfacespaced from the upper surface. The lower surface includes means foruniformly distributing a load applied to the clamp ring to components ofthe disk stack assembly underlying the clamp ring without damaging suchdisk stack assembly components on load-induced flexion of the clampring.

In a preferred form of the invention, the inner and outer walls are bothcylindrical and are uniformly spaced from one another. The loaddistributing means includes an arcuate rolling contact surface designedto permit points of contact between the lower surface of the clamp ringand the underlying disk stack assembly components to move duringload-induced flexion of the clamp ring without presenting a sharp edgewhich can damage or distort the underlying components. The radius of anarc of curvature of the arcuate rolling contact surface is greater thanthe outer diameter of the clamp ring. Moreover, the radius of the arc ofcurvature of the arcuate rolling contact surface is greater than twicethe inner diameter of the clamp ring.

A cantilevered section of the clamp ring is disposed radially inwardlyof the arcuate rolling contact surface. The cantilevered section isdefined by a portion of the lower surface disposed radially inwardly ofthe arcuate rolling contact surface and raised relative thereto so as tonot contact the disk stack components on load-induced flexion of theclamp ring. This portion of the lower surface is raised approximatelyten percent of the maximum height of the clamp ring.

In a process for assembling the clamp ring to the disk stack assembly,the clamp ring is first heated to increase the inner diameter thereof topermit the clamp ring to slip over the outer diameter of a hub for thedisk stack assembly. The clamp ring is then placed over the hub so thatthe arcuate rolling contact surface bears against the underlying diskstack components. An axial load is then applied to the clamp ring whichcauses it to flex, thus moving contact between the lower surface of theclamp ring and the underlying disk stack components radially along thearcuate rolling contact surface. The axial load is maintained until theclamp ring cools sufficiently to reduce the inner diameter thereof tofirmly clamp against the hub, at which time the axial load may beremoved from the clamp ring.

The construction of the clamp ring, and particularly the provision ofthe arcuate rolling contact surface, avoids the transfer of the axialload to the underlying disk stack components through a sharp corner ofthe clamp ring. This, advantageously, prevents distortion of theunderlying media which results when sharp corners are presented onflexion of the clamp ring under the applied load.

Other features and advantages of the present invention will becomeapparent from the following more detailed description, taken inconjunction with the accompanying drawings which illustrate, by way ofexample, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate the invention. In such drawings:

FIG. 1 is an exploded fragmented elevational sectional view through adisk drive unit disposed between upper and lower components of a diskclamp installation tool, illustrating, generally, the manner in whichthe disk clamp installation tool is utilized to assemble a clamp ringembodying the present invention to a disk stack assembly;

FIG. 2 is a bottom and side perspective view of the disk clampillustrated in FIG. 1;

FIG. 3 is an enlarged fragmented elevational sectional view takengenerally along the line 3--3 of FIG. 2, wherein the disk clamp has beeninverted back to its proper configuration for placement over a stack ofmemory storage disks;

FIG. 4 is a fragmented elevational sectional view similar to that shownin FIG. 3, illustrating flexion of the disk clamp as a force is appliedthereto during an assembly process; and

FIG. 5 is a flow chart illustrating the steps utilized to assemble theclamp ring to the disk stack assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown in the drawings for purposes of illustration, the presentinvention is concerned with an improved disk drive unit, generallydesignated in the accompanying drawings by the reference number 10. Thedisk drive unit 10 includes a spindle motor 12 for rotatably driving astack of memory storage disks 14 arranged to fit within the verticalprofile available to the disk drive unit 10.

The disk drive unit 10 comprises a so-called "hard" disk drive of thegeneral type used in modern personal computers and the like. The diskdrive unit 10 conventionally includes a substantially sealed housing 16defined by a rigid lower base 18 and a removable upper housing cover(not shown). The housing 16 has an overall size and shape with generallystandardized external dimensions selected to fit within a limitedinstallation envelope within a cabinet for a central processor unit of acomputer.

As is generally known in the art, the illustrative disk drive unit 10includes a head positioner assembly (not shown) mounted within thehousing 16 at a position alongside the disk stack. The head positionerassembly supports a plurality of individual arms having electro-magneticheads at the distal ends thereof in close proximity with respectiveupper and lower surfaces on the disks 14. A suitable actuator motor suchas a movable coil DC motor, and a corresponding motor controllerfunction to displace the heads through generally radial traversesrelative to the disks 14 for purposes of reading and writing data, allin a well known manner.

With reference to FIG. 1, a central shaft 20 is securely fixed to aportion of the housing lower base 16, and the memory storage disks 14are mounted for rotational movement within the housing 16 about theshaft 20. The shaft 20 includes a lower threaded end 22 that, typically,passes through the housing lower base 18 and is secured in place.

The shaft 20 is formed by machining or the like to accommodatepredetermined positional mounting of upper and lower bearing units 24and 26. More specifically, the two bearing units 24 and 26 comprise apair of precision ball bearing units each having an annular inner race28 cooperating with an annular outer race 30 to contain an annular arrayof bearing balls 32 therebetween. The upper bearing unit 24 ispositioned adjacent to an upper end of the shaft 20, and the lowerbearing unit 26 is positioned in a downward spaced relation to the upperbearing unit 24 toward a position with its inner race 28 seated againstan axially upwardly presented shoulder stop 34 on the shaft 20.

The outer races 30 of the two bearing units 24 and 26 rotatably supporta generally cylindrical hub core 36 constituting the rotor of thespindle motor 12. The outer race 30 of the upper bearing unit 24 issecured directly within an upper bore 38 of the hub core 36 in seatedrelation against a shoulder stop 40. Similarly, the outer race 30 of thelower bearing unit 26 is secured directly within a lower bore 42 of thehub core 36 in seated relation against a shoulder stop 44.

The rotary interfaces between the shaft 20 and the hub core 36 aresealed to prevent migration of bearing contaminants or the like intocontact with the memory storage disks 14. Although the specificstructure of the requisite sealing means may vary, a conventionallabyrinth seal 46 is utilized adjacent to the upper bearing unit 24, anda conventional exclusion ferro-fluid seal unit 48 is utilized adjacentto the lower bearing unit 26.

The hub core 36 supports, at its lower end, a plurality of permanentmagnets 50 which interact with an electro-magnetic stator core 52 torotate the hub core 36 about the shaft 20 in a known manner. The hubcore 36 also supports an outer disk supporting hub 54, which supportsthe stack of storage disks 14 for rotation within the disk drive housing16. In this regard, the disks 14 are stacked upon a lower outer supportflange 56 of the supporting hub 54. The disks 14 are separated from eachother by an intervening spacer ring 58 of precision height, therebyorienting the disks 14 in a precision spacing for access therebetween ofthe various heads discussed previously. An upper spacer ring 60 overliesthe uppermost disk 14, and a clamp ring 62, to be discussed in greaterdetail below, is fastened onto the upper end of the outer disksupporting hub 54 to compress the stack of disks 14 and related spacerrings 58 and 60. When so assembled, as the hub core 36 is driven duringmotor operation, the group of disks 14 are rotated as a collective unit.

In accordance with the present invention, and with reference to FIGS.2-4, the clamp ring 62 is preferably manufactured of an aluminum alloyand includes an inner cylindrical wall 64, an outer cylindrical wall 66which is uniformly spaced from the inner cylindrical wall, and upper andlower surfaces 68 and 70 which are spaced from one another and extendbetween the inner and outer walls. The lower surface 70 includes anarcuate rolling contact surface 72 that provides means for uniformlydistributing a load applied to the clamp ring 62 to components of a diskstack assembly underlying the clamp ring without damaging such diskstack components on load-induced flexion of the clamp ring. In thisregard, the disk stack assembly components include the underlyingportions of the memory storage disks 14 and the spacer rings 58 and 60.

A cantilevered section 74 of the clamp ring 62 is disposed radiallyinwardly of the arcuate rolling contact surface 72, and is defined by aportion of the lower surface 70 which is raised relative to the arcuaterolling contact surface 72 so as to not contact the underlying diskstack components on load-induced flexion of the clamp ring.

With reference to FIGS. 3 and 4, the exemplary clamp ring 62 has aninner diameter d at the inner cylindrical wall 64 of 0.9597 inch, and anouter diameter D at the outer cylindrical wall 66 of 1.250 inch. Thecenter of the arcuate rolling contact surface 72, indicated by the line76, has a diameter of 1.120 inch. The radius R of an arc of curvature ofthe arcuate rolling contact surface 72 is 2.0 inches. The overall heightof the clamp ring 62 is 0.050 inch, and the height of the cantileveredsection is 0.045 inch.

Typically, during installation of the clamp ring 62 over the outer disksupporting hub 54, a downwardly directed force is applied to the planarupper surface 68 of the cantilevered section 74. This downwardlydirected force causes flexion of the clamp ring 62 as illustrated inFIG. 4. Thus, the primary line of contact between the clamp ring 62 andthe underlying stack assembly component (the upper spacer ring 60)shifts from the intersection of the line 76 with the arcuate rollingcontact surface 72 to the intersection of the line 78 with the contactsurface 72. Advantageously, no sharp corner is presented by the clampring 62 during such flexion which could dig into and distort theunderlying media.

With reference once again to FIG. 1, an installation assembly isutilized to secure the clamp ring 62 about the supporting hub 52 overthe upper spacer ring 60. The installation assembly is shown in the formof a disk clamp installation tool comprising an upper ram 80 and a lowernest assembly 82. The nest assembly 82 is provided with a plurality ofhousing positioning pins 84 which engage apertures 86 in the housing 16of the disk drive unit 10, and a shaft positioning pin 88 that engagesthe lower threaded end 22 of the central shaft 20.

Referring now to FIG. 5, a process for assembling the clamp ring 62 to adisk stack assembly of the computer disk drive unit 10 is illustrated.First, as referenced in block 90, the clamp ring 62 is installed on theram 80 and heated to 410° F. The clamp ring 62 is heated to increase theinner diameter of the clamp ring at the inner wall 64, to permit it toslip over the outer diameter of the outer disk supporting hub 54. Whilethe clamp ring 62 is being heated, the disk drive unit 10 is placed ontothe nest assembly 82 to align the disk stack assembly of the disk driveunit 10 with the clamp ring 62 (block 92). When the clamp ring 62reaches 410° F., the heat is removed and the ram 80 is utilized toposition the clamp ring over the disk stack assembly and apply aseventy-five pound axial load thereto (block 94). Application of theseventy-five pound load will cause the clamp ring 62 to deflect, thusrolling the contact point between the arcuate rolling contact surface 72and the upper spacer ring 60 from the point indicated by the line 76 tothe point indicated by the line 78.

The axial load is maintained on the the clamp ring 62 and the underlyingdisk stack components until the clamp ring cools to a temperature below180° F. (block 96). This ensures that the inner diameter of the clampring 62 shrinks sufficiently to securely grip the outer diameter of thesupporting hub 54, thus preventing movement of the clamp ring 62relative to the supporting hub 54 and maintaining the seventy-five poundload on the underlying memory storage disks 14 and spacer rings 58 and60. The axial load is then removed from the clamp ring 62 (block 98),and the partially assembled disk drive unit 10 is then removed from thenest assembly 82 of the installation tool.

From the foregoing it will be appreciated that the novel clamp ring 62of the present invention provides effective means for uniformlydistributing a load applied to the clamp ring to components of the diskstack assembly underlying the clamp ring without damaging such diskstack components on load-induced flexion of the clamp ring. This isaccomplished by eliminating the possibility that a sharp corner of theclamp ring 62 can dig into and distort the underlying media which maycause malfunction of the disk drive unit.

Although a particular embodiment of the invention has been described indetail for purposes of illustration, various modifications may be madewithout departing from the spirit and scope of the invention.Accordingly, the invention is not to be limited, except as by theappended claims.

We claim:
 1. A clamp ring for assembly to a disk stack assembly of acomputer disk drive unit, comprising:an inner wall; an outer wall spacedfrom the inner wall; an upper planar surface extending from an upperedge of the inner wall to an upper edge of the outer wall; a lowersurface spaced from the upper planar surface and extending between theinner and outer walls, the lower surface including arcuate rollingcontact surface means for uniformly distributing a load applied to theclamp ring to components of the disk stack assembly underlying the clampring without damaging such disk stack assembly components onload-induced flexion of the clamp ring; and a cantilevered sectiondisposed radially inwardly of the arcuate rolling contact surface means,wherein the cantilevered section is defined by a portion of the lowersurface and the inner wall disposed radially inwardly of the arcuaterolling contact surface means and raised relative thereto so as to notcontact the disk stack assembly components on load-induced flexion ofthe clamp ring, wherein the radius of an arc of curvature of the arcuaterolling contact surface means is greater than an outer diameter of theclamp ring.
 2. The clamp ring of claim 1, wherein the inner wall iscylindrical, and the outer wall is cylindrical and uniformly spaced fromthe inner cylindrical wall.
 3. The clamp ring of claim 1, wherein theportion of the lower surface disposed radially inwardly of the arcuaterolling contact surface means is raised approximately ten percent of themaximum height of the clamp ring.
 4. The clamp ring of claim 2, whereinthe radius of the arc of curvature of the arcuate rolling contactsurface means is greater than twice an inner diameter of the clamp ring.5. A clamp ring for assembly to a disk stack assembly of a computer diskdrive unit, comprising:an inner cylindrical wall; an outer cylindricalwall uniformly spaced from the inner cylindrical wall; an upper planarsurface extending from the inner wall to the outer wall; a lower surfacespaced from the upper planar surface and extending between the inner andouter walls, the lower surface including arcuate rolling contact surfacemeans for uniformly distributing a load applied to the clamp ring tocomponents of the disk stack assembly underlying the clamp ring withoutdamaging such disk stack assembly components on load-induced flexion ofthe clamp ring; and a cantilevered section disposed radially inwardly ofthe arcuate rolling contact surface means, wherein the cantileveredsection is defined by a portion of the lower surface and the inner walldisposed radially inwardly of the arcuate rolling contact surface meansand raised relative thereto approximately ten percent of the maximumheight of the clamp ring so as to not contact the disk stack assemblycomponents on load-induced flexion of the clamp ring.
 6. The clamp ringof claim 5, wherein the radius of an arc of curvature of the arcuaterolling contact surface means is greater than an outer diameter of theclamp ring.
 7. The clamp ring of claim 5, wherein the radius of an arcof curvature of the arcuate rolling contact surface means is greaterthan twice an inner diameter of the clamp ring.
 8. A clamp ring forassembly to a disk stack assembly of a computer disk drive unit,comprising:an inner cylindrical wall; an outer cylindrical walluniformly spaced from the inner cylindrical wall; an upper planarsurface extending from an upper edge of the inner wall to an upper edgeof the outer wall; a lower surface spaced from the upper surface andextending between the inner and outer walls, the lower surface includingarcuate rolling contact surface means for uniformly distributing a loadapplied to the clamp ring to components of the disk stack assemblyunderlying the clamp ring without damaging such disk stack assemblycomponents on load-induced flexion of the clamp ring; and a cantileveredsection disposed radially inwardly of the arcuate rolling contactsurface means, wherein the cantilevered section is defined by a portionof the lower surface and the inner wall disposed radially inwardly ofthe arcuate rolling contact surface means and raised relative theretoapproximately ten percent of the maximum height of the clamp ring so asto not contact the disk stack assembly components on load-inducedflexion of the clamp ring, and wherein the radius of an arc of curvatureof the arcuate rolling contact surface means is greater than an outerdiameter of the clamp ring.
 9. The clamp ring of claim 8, wherein theradius of the arc of curvature of the arcuate rolling contact surfacemeans is greater than twice an inner diameter of the clamp ring.